[feat] add rtcp packet module

src/rtcp/rtcp_packet.cpp

@@ -0,0 +1,66 @@
+#include "rtcp_packet.h"
+
+#include "log.h"
+
+#define IP_PACKET_SIZE 1500  // we assume ethernet
+
+bool RtcpPacket::OnBufferFull(std::vector<uint8_t>& packet,
+                              PacketReadyCallback callback) const {
+  if (packet.empty()) {
+    return false;
+  }
+  callback(packet);
+  return true;
+}
+
+size_t RtcpPacket::HeaderLength() const {
+  size_t length_in_bytes = BlockLength();
+
+  if (length_in_bytes <= 0) {
+    LOG_FATAL("length_in_bytes must be a positive value");
+    return -1;
+  }
+
+  if (length_in_bytes % 4 != 0) {
+    LOG_FATAL("Padding must be handled by each subclass, length_in_bytes [{}]",
+              length_in_bytes);
+    return -1;
+  }
+  // Length in 32-bit words without common header.
+  return (length_in_bytes - kHeaderLength) / 4;
+}
+
+// From RFC 3550, RTP: A Transport Protocol for Real-Time Applications.
+//
+// RTP header format.
+//   0                   1                   2                   3
+//   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+//  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+//  |V=2|P| RC/FMT  |      PT       |             length            |
+//  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+void RtcpPacket::CreateHeader(
+    size_t count_or_format,  // Depends on packet type.
+    uint8_t packet_type, size_t length, uint8_t* buffer, size_t* pos) {
+  CreateHeader(count_or_format, packet_type, length, /*padding=*/false, buffer,
+               pos);
+}
+
+void RtcpPacket::CreateHeader(
+    size_t count_or_format,  // Depends on packet type.
+    uint8_t packet_type, size_t length, bool padding, uint8_t* buffer,
+    size_t* pos) {
+  if (length >= 0xffffU) {
+    LOG_FATAL("length must be less than 0xffffU");
+  }
+  if (count_or_format >= 0x1f) {
+    LOG_FATAL("count_or_format must be less than 0x1f");
+  }
+  constexpr uint8_t kVersionBits = 2 << 6;
+  uint8_t padding_bit = padding ? 1 << 5 : 0;
+  buffer[*pos + 0] =
+      kVersionBits | padding_bit | static_cast<uint8_t>(count_or_format);
+  buffer[*pos + 1] = packet_type;
+  buffer[*pos + 2] = (length >> 8) & 0xff;
+  buffer[*pos + 3] = length & 0xff;
+  *pos += kHeaderLength;
+}